Synthesis of NiMo catalysts supported on mesoporous Al2O3 with different crystal forms and superior catalytic performance for the hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene

Mesoporous Al2O3 (MA) materials with different crystal forms were synthesized from the boehmite sol. A series of MA materials were used as supports for sulfided NiMo catalysts in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The as-synthesized MA materials with different crystal forms and the corresponding NiMo catalysts were characterized using XRD, nitrogen physisorption, FTIR, pyridine FTIR, UV–vis, Raman, H2 TPR, XPS, and HRTEM characterization methods. The NiMo/δ-Al2O3 (NiMo/δ-MA) catalyst exhibited the highest DBT and 4,6-DMDBT conversion at all the weight hourly space velocities (WHSVs); moreover, its DBT conversion (99.6%) was about twice that of the commercial NiMo/Al2O3 (NiMo/C-MA) catalyst (50.2%), while its 4,6-DMDBT conversion (65.8%) was more than four times that of the NiMo/C-MA catalyst (15.5%) at 613 K, 4.0 MPa, 200 ml/ml, and 150 h−1. The superior catalytic performance of the NiMo/δ-MA catalyst could be ascribed to the synergistic effect of desirable textural properties, moderate acidity, suitable metal–support interaction, appropriate dispersion, and excellent stacking morphology of the active phases. 4,6-DMDBT HDS over the NiMo/δ-MA catalyst showed the highest HYD/DDS ratio (3.08), indicating that the HYD pathway was the main reaction route. Furthermore, an HDS reaction network was proposed for 4,6-DMDBT over NiMo/δ-MA.